Method for producing a bacteriostatic finish on synthetic fabrics



United States Patent 3,498,829 METHOD FOR PRODUCING A BACTERIOSTATIC FINISH ON SYNTHETIC FABRICS Leonard Lilland, Wellesley, and Emil Moser-Vincekovic, Watertown, Mass., assignors to The Kendall Company, Boston, Mass., a corporation of Massachusetts No Drawing. Filed Oct. 19, 1967, Ser. No. 676,651 Int. Cl. D06n 3/00; B44d N22 US. Cl. 117-138.5 5 Claims ABSTRACT OF THE DISCLOSURE A phenolic bacteriostatic agent is dispersed in a liquid medium either as a true solution or as an ultra-fine dispersion. Fabrics comprising synthetic fibers are impregnated with the liquid, dried, and cured at at least 120 C. The curing process promotes a thermal diffusion of the bacteriostatic agent into the synthetic fabric substance, whereby a bacteriostatic finish durable to laundering is produced.

This invention relates to a process for developing a nontoxic, nonirritating bacteriostatic finish, durable to laundering, on textile materials comprising synthetic polymeric fibers, or filaments such as nylon, polyester, spandex, polyacrylic, and modacrylic fibers, blends of such fibers, or blends of such fibers with other fibers.

It is generally recognized that the development of unpleasant odors in textile fabrics which come in contact with the human body is due to the action of skin bacteria on perspiration or perspiration residues. The resident bacterial flora on the skin of normal, healthy individuals is estimated to run as high as 10,000 per square centimeter. This bacterial population resides chiefly on the surface of the skin, varies in number from place to place, and is 'believed responsible for the development of odors from perspiration, which as exuded by the normal body is sterile and odorless. It has long been a goal of textile technologists to develop a safe and effective bacteriostatic finish for textile fabrics intended for contact with the human body.

Although literally hundreds of products are known to exert a bacteriostatic or even bactericidal action toward normal and pathogenic bacterial flora, the majority of them are unsuitable for use as a finish intended for textiles to be laundered and reused on the body. Many are irritants.

Others are so insoluble in water as to be effective only in organic solvent solution. Others, on the contrary, are so water-soluble as to leach right out of the fabric and resist fixation thereto.

Still others, such as certain heavy metal salts, are definitely toxic to the human system.

One compound which is very effective as a bacteriostatic agent, and which shows no incidence per se of skin irritation, is hexachlorophene, or 2,2'-dihydroxy- 3,5,6,-3',5',6'-hexachloro diphenyl methane. This white crystalline compound, although soluble in a variety of organic solvents, is insoluble in water. When applied to a fabric from organic solution and dried, hexachloro phene is deposited as a residue which shows bacteriostatic action. However, the hexachlorophene is merely physically present on the fabric, without more than the most superficial fixation thereto: mechanical manipulation of the fabric with laundering and the emulsifying action of soaps or detergents, will rapidly remove the insoluble and unfixed reagent and leave the fabric unprotected.

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This type of transient effect will often not even survive the rigors of laying-out, cutting, fabricating, packing, shipping and displaying garments made from fabrics treated with organic solutions of hexachlorophene.

In US. Patent application Ser. No. 632,927, filed Apr. 24, 1967, now abandoned, of common assignee, there is described a process whereby phenolic bacteriostatic agents such as hexachlorophene can be durably bound to fabrics composed of cellulosic fibers or yarns by the complexing action of zirconium acetate. Fabrics thus treated show a durable suppression of bacterial growth after as many as 5 0 launderings.

The accepted use of synthetic fibers, alone, blended or in blends with other fibers, in garments, linings, interlinings, blankets and the like, make it very desirable that a durable bacteriostatic finish be developed to use on synthetic textile substrates.

It is with improvements in the art of fixing phenolic bacteriostatic agents, particularly biphenolic substances such as hexachlorophene, to synthetic textile substrates that the present invention is concerned. It is a primary object of the invention to provide a process for fixing biphenolic bacteriostatic agents to synthetic textile substrates in a manner which will survive numerous laundermgs.

It has been found that if a woven or nonwoven fabric composed of nylon, polyester, spandex, acrylic, or modacrylic fibers or filaments is treated with a liquid solution or ultra-fine dispersion containing zirconium acetate and hexachlorophene solubilized by wetting agents, dried and cured briefly at C., no durable bacteriostatic effect is developed on the fabric.

When the process was repeated using temperatures of 150C. to 175 C., however, the results were in sharp contrast. Nylon, polyacrylic, spandex, and modacrylic fabrics showed, at this elevated cure temperature, a bac teriostatic effect which survived multiple launderings. Since it is believed that hexachlorophene and zirconium acetate react at temperatures below C., it was postulated that the method of attachment of hexachlorophene to synthetic fabric substrates must follow a different mechanism from the attachment to cellulosic fabrics by means of zirconium acetate. Accordingly, the acetate was omitted from a series of experiments, hexachlorophene being cured onto the fabric at temperatures of about 120 C. Surprisingly, the absence of the zirconium acetate had no adverse effect on the durability of the bacteriostatic finish developed. Further investigation revealed that on certain synthetic polymeric materials, a durable bacteriostatic finish could be produced by what is presumably a thermal diffusion of the bacteriostatic agent into the polymer. It will be apparent that a reaction of this sort is dependent on both time and temperature. Some effect is noted at temperatures as low as 50 C. if the curing time is prolonged to 20 hours, under which conditioins about 10% of the originally-applied bacteriostatic agent will remain on the fabric after 6 launderings. At 100 C. and 30 minutes cure, 25% of the applied agent remains after 10 launderings. These conditions are about the minimum practical operating conditions. At increased temperatures the necessary cure time drops off drastically, a preferred set of conditions for continuous operation without danger of discoloration being a cure at 120 C.- C. for 3 to 10 minutes.

The preferred process of this invention, therefore, comprises:

(1) Preparing a liquid dispersion or solution of a biphenolic bacteriostatic agent in the form of an aqueous solution of the agent solubilized by nonionic wetting agents; an organic solution; an aqueous-organi solution; or an ultra-fine colloidal dispersion of the agent.

(2) Padding an amount of the solution or dispersion onto a synthetic fabric substrate in an amount sufficient to give between 0.2% and 2% of the agent on the fabric.

(3) Drying the treated fabric to give a coating of bacteriostatic agent in ultra finely divided form on the fibers or filaments.

(4) Curing the fabric carrying the finely-divided bacteriostatic agent at a temperature of at least about 120 C.- 140 C. for a period of at least 3 to 10 minutes.

An effective method of preparing an aqueous solution of hexachlorophene is to dissolve 1 part of the bacteriostatic agent, with stirring, in 4 parts of nonionic detergent. For the detergent, a mixture of 3 parts of Igepal CO-850 (trademark of General Aniline) and 1 part of Triton X100 (trademark of Rohm and Haas) is especially satis factory in giving a clear solution which is diluted with water to make 100 parts.

Drying and curing may conveniently be carried out by means of conventional devices such as high-pressure steam cans, gas-fired or electrically heated ovens, infra red, and the like.

In evaluating the presence of hexachlorophene remaining on the fabric after multiple launderings, two methods are employed. Bacteriostatic efiiciency is measured by placing disks of the treated and laundered fabric on agar plates inoculated with bacillus subtilis or staphylococcus aureus, and noting the zone of inhibition of bacterial growth in the vicinity of the fabric disk. A quantitative determination of the amount of hexachlorophene present on the fabric is made by extracting the fabric with 0.1 N potassium hydroxide, in which it is soluble. Hexachlorophene absorbs strongly at 320 millimicrons in a U.V. spectrophotometer, and the absorbence is proportional to the concentration of the hexachlorophene. By matching the absorbence of text extract against a set of standards, the amount of hexachlorophene on a fabric can be determined.

The invention may be illustrated by the following examples.

E AMPLE I A fabric composed of nylon yarns was padded to 75% pickup of a 1% solution of hexachlorophene solubilized in water by 4% nonionic wetting agent, as set forth above. Two samples of the fabric were dried and cured, one at 150 C. and the other at 170 C., each for 5 minutes. After repeated launderings, the percent of the hexachlorophene remaining on the fabric was determining by the potassium hydroxide extract, as explained above.

Nylon150 C. cure Percent of hexachlorophene Launderings: remaining on fabric 100 2 50 33 30 The 50% decrease in hexachlorophene content in the first two launderings is largely attributed to the removal of excess unbound-i.e., not adsorbedhexachlorophene, since the fabrics were not afterwashed after the curing process.

Nylon170 C.

Percent of hexachlorophene Launderings: remaining on fabric 0 100 4 EXAMPLE 11 When a spandex-nylon fabric was treated in the same manner and cured at.150 C., the following results were noted:

Percent of hexachlorophene Launderings: remaining on fabric 0 3 52 5 48 15 44 25 36 Both the nylon yarns and the spandex yarns were actively bacteriostatic after repeated launderings.

EXAMPLE III A similar experiment was run on a sample of an allacrylic needled blanket, with the following results:

Acrylic blanket- C.

Percent of hexachlorophene Even after 40 launderings, the disks of the acrylic blanket showed inhibition of bacterial growth when placed on inoculated culture plates. Results similar to the above were obtained using modacrylic fabrics.

When the procedure was repeated using a polyester fabric, however, curing at 0., did not result in a durable bacteriostatic finish, no trace of hexachlorophene being left after 5 launderings. No improvement was noted when zirconium acetate was added to the hexachlorophene treating solution.

Using an aqueous solution of 1% hexachlorophene in a 50-50 by volume mixture of acetone and water, and repeating the pad, dry, and cure at 160 C. process as above, the following excellent durable bacteriostatic finish was developed on a polyester fabric:

EXAMPLE IV Polyester160 C.

Percent of hexachlorophene Launderings: remaining on fabric 0 100 The above level of activity indicates that the polyester fabric will remain actively bacteriostatic after 40 or 50 launderings.

Similar results were obtained when the hexachlorophene was dissolved in pure acetone, but aqueous solutions of acetone or other water-miscible solvents for the bacteriostatic agent are preferred on account of their lower flammability.

As an alternative procedure for polyester fabrics, a very fine colloidal dispersion of hexachlorophene is prepared by dissolving 1 part of hexachlorophene in 2 parts of acetone and adding, gradually and with stirring, a solution of 2 parts of acetic acid and 0.3 part of Triton X-l00 in 94.7 parts of water. This dispersion was padded onto a polyester fabric, and exposed to 135 C. for 7 minutes to dry and cure the fabric. Analysis showed:

EXAMPLE V Percent hexachlorophene Launderings: remaining on fabric 100 1 50 5 40 A lever of 20% after 20 launderings (0.1% hexachlorophene on the weight of the fabric) is an efi'ective bacteriocidal finish.

To demonstrate the effectiveness of the above treatment on blended fabrics, the treating dispersion set forth immediately above of 1 part hexachlorophene, 2 parts acetone, 2 parts acetic acid, 0.3 part of Triton, and 94.7 parts of water was diluted with two volumes of water to yield a dispersion containing about 0.3% hexachlorophene. This was padded onto a 50% 50% polyester-cotton fiber-to-fiber blend poplin fabric, at about 100% pickup, dried and cured at 135 C. for 7 minutes. Analysis showed:

EXAMPLE VI Percent hexachlorophene Launderings: remaining on fabric 0 100 1 46 5 30 10 20 18 In a parallel experiment on an all-cotton fabric, no hexachlorophene was detectable after 5 launderings.

The exact reason why hexachlorophene is fixed to nylon and acrylic fabrics under conditions which show no permanent attachment of hexachlorophene to polyester fabrics is probabily complex. It is apparently important that the hexachlorophene be deposited onto the fabric from a true solution or from an ultra-fine colloidal dispersion. If a crude dispersion, containing coarsely-particulate hexachlorophene, is used, durability to repeated laundering is greatly reduced.

Additionally, the permeability of the fiber or filament should be taken into consideration, polyesters in general being more refractory than nylon, acrylic, or spandex. Finally, the presence of a wetting agent appears to interfere with the diffusion of a bacteriostatic agent into polyester fibers in a manner which is not true of nylon, spandex, acrylics, or modacrylics.

To verify this, a polyester fabric was impregnated with a solution of hexachlorophene in acetonewater, as above. It was then carefully wet with an aqueous solution of a nonionic wetting agent, dried and cured for 5 minutes at 160 C. No durable-to-laundering bacteriostatic effect was obtained, whereas the effect was very durable in the absence of the wetting agent. Appatently the competitive reaction between solubility in wetting agent and thermal diffusion into the snythetic substrate will, as in the case of dyestuffs, vary with the chemical nature of the synthetic material.

Atlhough a 5050 mixture by volume of acetone and water was used in the example of durable effects on polyester fabrics, the invention is not confined to those proportions nor to acetone. Methanol and other watermiscible solvents such as other lower aliphatic ketones and alcohols may be used, in varying proportions, provided that the hexachlorophene is present in the organic or aqueous-organic medium in true solution or as an ultra-fine colloidal dispersion.

Also, although hexachlorophene has been used as the examplary bacteriostatic agent throughout the above description, other bifunctional (biphenolic) agents may be used, such as bithionol, which is his (2-hydroxy-3,5-dichlorophenyl) sulfide, or G4, which is bis (S-chloro-Z- hydroxy phenyl) methane.

It will be apparent to those skilled in the art that in the case of very tight and heavy weaves, it may be necessary to operate at the upper ranges of time and temperature of cure, in order to insure that the interior portions of the fabric are brought to temperature for a sufficient interval.

Having thus described our invention, we claim:

1. The method of producing a durable, launder-resistant bacteriostatic finish on synthetic textile materials comprising fibers selected from the class consisting of nylon, spandex, polyester, acrylic, and modacrylic fibers; blends of such fibers, and blends of such fibers with other fibers, which comprises applying to the fabric from an essentially aqueous medium a bacteriostatically-effective amount of hexachlorophene, drying the fabric to produce a coating of the hexachlorophene in ultra-finely divided form, and heating said fabric to a temperature of at least C.,

thereby promoting thermal diffusion of said hexachlorophene into said synthetic fabric.

2. The method according to claim 1 in which the essentially aqueous medium is an aqueous solution of hexachlorophene solubilized by a nonionic wetting agent.

3. The method according to claim 1 in which the essentially aqueous medium is a solution of hexachlorophene in a mixture of water and a water-miscible solvent selected from the class consisting of the lower aliphatic ketones and alcohols.

4. The method according to claim 1 in which the heating period is between at least C. and C. for 3 to 10 minutes.

5. The method of producing a durable, launder-resistant bacteriostatic finish on a fabric comprising polyester fibers which comprises applying to the fabric a dilute solution of hexachlorophene in a mixture of water and an organic solvent selected from the class consisting of the lower aliphatic ketones and alcohols,

removing excess liquid from the fabric,

drying the fabric,

and curing the fabric at about C. for about 5 minutes.

References Cited UNITED STATES PATENTS 2,633,446 3/1953 King 117138.5 X 2,999,047 9/1961 Model et al 117l38.5 X 3,162,572 12/1964 Granouist et al. l6738.7 2,250,480 7/1941 Gump 260-619 3,183,149 5/1965 Gonzales et al. 8116 2,830,011 4/1958 Parker et al. 117-1385 X 3,183,149 5/1965 Gonzales et a1 8-116 2,557,172 6/1951 Brooks 117-138.5 X

WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS, Assistant Examiner US. Cl. X.R.

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